III-Nitride nanowire array monolithic photonic integrated circuit on (001)silicon operating at near-infrared wavelengths

ABSTRACT

Photonic devices such as semiconductor lasers and photodetectors of various operating wavelengths are grown monolithically on a Silicon substrate, and formed of nanowire structures with quantum structures as active regions. A reduction of strain during fabrication results from the use of these nanowire structures, thereby allowing devices to operate for extended periods of time at elevated temperatures. Monolithic photonic devices and monolithic photonic integrated circuits formed on Silicon substrates are thus provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.62/549,412, entitled “III-Nitride Nanowire Array Monolithic PhotonicIntegrated Circuit On (001)Silicon Operating At Near-InfraredWavelengths” and filed Aug. 23, 2017, which is incorporated herein byreference in its entirety.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grantsECCS-1648870 and DMR-1120923 awarded by the National Science Foundation.The government has certain rights in the invention.

FIELD OF THE DISCLOSURE

The present disclosure relates to solid-state semiconductor devices and,more specifically, to the monolithic growth of nanowire array quantumstructures on Silicon (Si) substrate and photonic devices formedthereof.

BACKGROUND

Every year electronic devices become faster. This happens because ofMoore's law which states that transistors, which are the major elementof all electronic circuits, become smaller every year. This trendresults in a higher density of the number of transistors that can befabricated on a microchip. One of the biggest technological concerns ofthe 21^(st) century is the possible saturation of Moore's law and as aconsequence the improvement of device speed with time may come to anend.

Many techniques have been suggested to keep Moore's law relevant. One ofthem is the incorporation of photonic devices on Silicon (Si)microchips, which would further improve the speed of the next generationdevices such as microchips and integrated circuits, with light beingmuch faster than electricity.

Currently, the main high-volume industrial manufacturing technology thatis used to produce integrated circuits, such as electronic microchipsand computer microprocessors, is Complementary Metal-Oxide-Semiconductor(CMOS) technology. Current CMOS microchips in the microelectronicsindustry are based on (001) Silicon (Si) substrates. Hence initialphotonic devices also have to be compatible with (001) Silicon.Unfortunately, Si itself cannot emit light. To circumnavigate thisproblem, in conventional systems, lasers made of other materials havebeen fabricated separately and then placed on the Si substrate.

SUMMARY OF THE INVENTION

The present techniques include methods of fabricating photonic devices,such as semiconductor diode lasers, formed of nanowire structures grownmonolithically on a Silicon substrate, and in particular on a (001)Silicon substrate. The photonic devices may be monolithically grown bygrowing an array of III-V nanowires directly from the (001) Siliconsubstrate in a single epitaxial growth process. The result is amonolithic structure in which a nanowire array of one type ofsemiconductor material is grown extending from a substrate of anothersemiconductor material, in particular Silicon.

In some examples, monolithically grown nanowires are grown as an arrayof nanowires, where the array may be formed into different photonicdevices. In some examples, the photonic devices are edge emitting lasersformed from nanowires monolithically grown in the Silicon substrate. Insome examples, the photonic devices are vertical cavity surface emittinglasers formed from nanowires monolithically grown in the Siliconsubstrate. The lasers may operate for extended periods of time undercontinuous wave or pulsed operation at elevated temperatures. Otherphotonic devices formed of these monolithically grown nanowire arraysinclude photodetectors.

Instead of traditional planar epitaxial layers, in some examples, thepresent techniques are able to form by monolithically grown nanowireshaving quantum structures that form the active gain region of a laser orform the absorption region in a photodetector. In these examples,monolithic growth may be achieved through the growth of nanowires, fromwhich monolithic photonic devices are thereby formed from thesenanowires. A reduction of strain results from using nanowire structuresand that has made it possible for these devices to be formedmonolithically on Silicon substrate and for these devices to operateunder continuous wave or pulsed mode of operation for extended periodsof time at elevated temperatures. In other words, in various examples,photonic devices are thermally stable and their performance does notdegrade significantly with increasing temperatures.

In some examples, the present techniques provide a complete monolithicphotonic integrated circuit directly grown on (001) silicon. In someexamples, the circuit includes a diode laser, dielectric waveguide, andphotodetector. The diode laser may be an edge-emitting laser and thephotodetector a guided-wave photodiode, where both are fabricated of thesame III-nitride nanowire arrays, providing more flexibility to thesedevices.

The present techniques also include the fabrication of a nitride-basednanowire array photodiode on silicon. For example, in someimplementations, a nanowire array photodiode may be formed exhibiting alarge responsivity at 1.3 μm, making the photodiodes ideal for siliconphotonics and on-chip communication, as described. The photodiodes maybe realized with the same monolithic nanowire array as used to form amonolithic semiconductor laser, but the photodiode may be operated underreverse bias, in contrast the semiconductor laser which is operatedunder forward bias.

The present techniques further provide the fabrication of a monolithiclaser, which can be used for coherent light optical communication,inter-chip or intra-chip. The present techniques provide for lasers withemission wavelength of 1.3 μm, which is a desirable wavelength, as thisparticular wavelength produces low light dispersion in SiO₂ and istransparent to silicon. This wavelength also allows eye-safe operation.

The present techniques further provide the first monolithic photonicintegrated circuit directly grown on (001) silicon substrate. In someexamples, a photonic integrated circuit may be formed of a monolithicsemiconductor laser having emission wavelength at or around 1.3 μm and adetector having 0.1 A/W responsivity at 1.3 μm, each grown on a (001)silicon subsrate. In some examples, the active material of the laser anddetector is an array of InN/InGaN/GaN heterostructure nanowires. In someexamples, InN disks have been inserted in GaN nanowires and this enableslaser emission and detector absorption at 1.3 μm in the photonicintegrated circuit.

The photonic integrated circuit is useful in silicon photonics basedapplications, i.e., on-chip communication etc. The laser output power,detector responsivity, and overall response of the photonic integratedcircuit is sufficiently large for such applications. The lasers showhigh temperature stability, and good differential gain. The detectorphotocurrent response follows the laser injection current well,demonstrating a successful photonic integrated circuit on (001) Si.These characteristics can be exploited in a variety of applicationswhere the environment can be challenging, e.g., smart car enginesystems.

In some examples, the present techniques provide particular advantagesover conventional systems. Graded layer regions have been grown inIII-Nitride nanowire laser structures. The growth of InN disks as theactive region has been achieved, thus providing for emissions in thenear infrared, e.g., at 1.3 μm. A III-nitride nanowire photodiodeoperating at near-infrared using InN disks has been demonstrated. Theexternal deposition of a dielectric to form a waveguide in between amonolithically grown nanowire laser and a monolithically grown nanowirephotodetector to fabricate a complete photonic integrated circuit hasbeen shown.

In accordance with an example, a semiconductor device comprises: aSilicon (Si) substrate; and a III-Nitride nanowire structure having (i)a quantum region formed of one or more layers of InN quantum disks, (ii)a first graded layer region, and (iii) a second graded layer region,wherein the quantum region is located between the first graded layerregion and the second graded layer region, and wherein the III-Nitridenanowire structure is monolithically grown from the Si substrate, andwherein the III-Nitride nanowire structure is responsive at or about 1.3μm.

In accordance with another example, a nanowire array structurecomprises: a Silicon (Si) substrate; and a plurality of III-Nitridenanowire structures each having (i) a quantum region formed of one ormore layers of InN quantum disks, (ii) a first graded layer region, and(iii) a second graded layer region, wherein the quantum region islocated between the first graded layer region and the second gradedlayer region, wherein the plurality of III-Nitride nanowire structuresare monolithically grown from the Si substrate, and wherein theplurality of III-Nitride nanowire structures are responsive at or about1.3 μm.

In accordance with another example, a photonic integrated circuitcomprises: a Silicon (Si) substrate; a first plurality of III-Nitridenanowire structures each having (i) a quantum region formed of one ormore layers of InN quantum disks, (ii) a first graded layer region, and(iii) a second graded layer region, wherein the quantum region islocated between the first graded layer region and the second gradedlayer region, wherein the first plurality of III-Nitride nanowirestructures are monolithically grown from the Si substrate, and whereinthe first plurality of III-Nitride nanowire structures form a nanowiresemiconductor laser capable of emitting a photonic output at or about1.3 μm; and a second plurality of III-Nitride nanowire structures eachhaving (i) a quantum region formed of one or more layers of InN quantumdisks, (ii) a first graded layer region, and (iii) a second graded layerregion, wherein the quantum region is located between the first gradedlayer region and the second graded layer region, wherein the secondplurality of III-Nitride nanowire structures are monolithically grownfrom the Si substrate, and wherein the second plurality of III-Nitridenanowire structures form a nanowire semiconductor photodetector capableof absorbing a photon input at or about 1.3 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a nanowire quantum semiconductor laser and a nanowirequantum semiconductor detector both monolithically grown on a Siliconsubstrate forming a monolithically fabricated photonic integratedcircuit, in accordance with an example.

FIG. 2 depicts an example of the nanowire quantum semiconductor laser ofFIG. 1 and, in particular, showing a nanowire array structure within thelaser, in accordance with an example.

FIG. 3A depicts a Scanning Electron Microscope (SEM) image of amonolithically grown semiconductor laser device, in accordance with theexample of FIG. 2.

FIG. 3B depicts a SEM image of an InGaN/GaN disk-in-nanowire arrayformed of multiple nanowires structures clustered together, inaccordance with an example.

FIG. 4 illustrates the epitaxial crystal structure of a monolithicallygrown nanowire array semiconductor laser, in accordance with an example.Depicted in the diagram are various crystal layers within a nanowirestructure, in particular, an example epitaxial crystal structure of anindividual InN/In_(0.4)Ga_(0.6)N/GaN heterostructure nanowire, capableof emitting in the visible (530 nm) and included within an array ofdensely packed nanowire structures monolithically grown on (001) Sisubstrate, in accordance with an example.

FIG. 5 depicts the epitaxial crystal structure of another examplemonolithically grown nanowire semiconductor laser, in particular showinga laser capable of emitting at a near infra-red wavelength of at orabout 1.3 μm, in accordance with an example.

FIG. 6 depicts Light-Current (L-I) characteristic plots of a broad areanear infra-red (NIR) semiconductor laser devices with emissionwavelength of about 1.3 μm, in accordance with an example herein. Theinset shows the output spectral characteristics for an injection currentof 810 mA. The plot depicts the steady-state L-I characteristics at roomtemperature of an example 50 μm×2 mm ridge waveguide laser operatingunder Continuous Wave (CW) and pulsed (5% duty cycle) modes ofoperation. Output powers up to ˜10 mW were measured at room temperaturewithout any heat sinking or facet cooling. The output spectrum depictedin the inset confirms 1.3 μm peak emission. The slope efficiency was0.14 W/A. A low value of threshold current I_(th)=673 mA was measured.The laser emission wavelength was in the near infra-red range of thespectrum at a wavelength of about 1.3 μm.

FIG. 7 depicts a plot of temperature dependence of the threshold currentdensity J_(th) for a nanowire semiconductor laser having an emission inthe near infra-red range of at or about 1.3 μm, in accordance with anexample.

FIG. 8 depicts a plot of measured output power versus time (for acontinuous wave current injection) for a 1.3 μm nanowire semiconductorlaser formed as a disk-in-nanowire semiconductor quantum laser, inaccordance with an example. These measurements were made without anyheat sinking or active cooling. The data indicates a lifetime of ˜1000hours, albeit much high lifetimes are achievable.

FIG. 9 is a SEM image of a monolithically grown photonic integratedcircuit formed of arrays of nanowire structures. Specifically, anedge-emitting semiconductor laser and a guided-wave nanowire photodiodeare formed with the same nanowire array and SiO₂/Si₃N₄ dielectricwaveguide is formed in between the laser and the photodetector. Theinset on the lower left corner of the picture depicts a magnified imageof an air/nanowire Distributed-Bragg-reflector (DBR) mirror formed byFocused-Ion-Beam (FIB) etching technique.

FIGS. 10A and 10B depicts a SEM image (top image FIG. 10A) and anoptical microscope image (bottom image FIG. 10B) of a photonicintegrated circuit, in accordance with an example. Note that the sizescales of the two images are not the same. Similar to FIG. 16, thephotonic integrated circuit includes a semiconductor laser, a linearwaveguide structure, and a semiconductor photodetector. Thesemiconductor laser and the semiconductor photodetector are both III-GaNnanowire array structures that are formed monolithically on a Siliconsubstrate.

FIG. 11 depicts a process of fabricating a photonic integrated circuitformed of monolithically grown nanowire structures, in accordance withan example.

FIGS. 12A and 12B schematically illustrate fabricated nanowire arraysmonolithically grown on a (001) Si substrate, as part of the photonicintegrated circuit fabrication process of FIG. 11, in accordance with anexample. FIG. 12A illustrates the formation of epitaxial crystal growthlayers in the nanowire array using a plasma assisted molecular beamepitaxy (PA-MBE) technique; and FIG. 12B illustrates a Paryleneplanarization process from FIG. 11, in accordance with an example.

FIGS. 13A and 13B illustrate further processing in accordance with FIG.11. FIG. 13A illustrates fabrication after a p-metal deposition over aselected array of the nanowire array has occurred. FIG. 13B illustratesfabrication after an etching of the nanowire array has been performed toform a channel resulting in two spaced apart nanowire arrays, inaccordance with an example.

FIGS. 14A and 14B illustrate further processing in accordance with FIG.11. FIG. 14A illustrates fabrication after an n-metal deposition hasbeen performed over selected areas of the exposes n-Silicon substrate.FIG. 14B illustrates fabrication after waveguide layers have beendeposition is a channel between nanowire arrays, e.g., between ananowire array forming a semiconductor laser and a nanowire arrayforming a photodetector.

FIG. 15 depicts a schematic illustration of a formed photonic integratedcircuit that includes a nanowire semiconductor laser and a nanowiresemiconductor photodetector with a linear waveguide structure betweenthe two devices.

DETAILED DESCRIPTION

The present techniques include methods of fabricating photonic devices,such as semiconductor lasers and photodiodes, formed of nanowirestructures grown monolithically on a Silicon substrate, and inparticular on a (001) Silicon substrate. The devices are monolithicallygrown by growing an array of III-V nanowires directly from the (001)Silicon substrate in a single epitaxial growth process. The result amonolithic structure in which a nanowire array of one type ofsemiconductor material is grown extending from a substrate of anothersemiconductor material, in particular Silicon.

In some examples, these monolithically grown nanowires are grown as anarray of nanowires, where the array may be formed into differentphotonic devices. In some examples, the photonic devices are edgeemitting lasers formed from nanowires monolithically grown in theSilicon substrate. In some examples, the photonic devices are verticalcavity surface emitting lasers formed from nanowires monolithicallygrown in the Silicon substrate. The lasers may operate for extendedperiods of time under continuous wave or pulsed operation at elevatedtemperatures. Other photonic devices formed of these monolithicallygrown nanowire arrays include photodetectors.

In various examples, as described, III-nitride nanowire lasers andphotodiodes are monolithically grown, having identical heterostructuresand constituent material sections. In this way, these structures areable to form a monolithically grown photonic integrated circuit that canbe realized by one-step epitaxy on (001) silicon substrates, addingsignificant flexibility to device and circuit fabrication. Whilenanowire arrays have been incorporated in the design of lasers emittingin the visible range, the nanowire heterostructure described in variousexamples herein are different in fundamental ways. Nanowireheterostructures in some examples herein are formed of: (i) InN disksinserted to form the light emission/absorption region of the respectivedevices; and (ii) graded InGaN regions incorporated for strain balancingin the heterostructure, reduction of defect density and optimal guidingof light in the lasers and detectors.

Further still in various examples herein, the present techniques includethe fabrication of a nitride-based nanowire array lasers and photodiodesmonolithically grown on silicon. In particular, nanowire array lasersand photodiodes exhibiting large responsivity at 1.3 μm are shown.

From the formation of such elements, the present techniques furtherprovide the monolithic photonic integrated circuit directly grown on(001) silicon substrate. Many applications can use near-infrared (NIR)lasers and photodiodes operating at wavelengths of ˜1.3 μm. Theseinclude such electronic applications as on-chip and off-chipcommunication to design faster processors and computers. Together with awaveguide and detector these lasers can serve as a complete on-chipmonolithic photonic link or optical interconnect. FIGS. 1 and 2illustrate an example photonic integrated circuit (PIC) formedmonolithically on a Silicon substrate.

FIG. 1 depicts a monolithically grown nanowire quantum semiconductorlaser and a monolithically grown nanowire quantum semiconductor detectorboth grown on a Silicon substrate and both combing to form amonolithically fabricated photonic integrated circuit 100. In theillustrated example, the integrated circuit 100 is formed of a curvedwaveguide in addition to a laser and a detector.

More specifically, in the illustrate example, photonic integratedcircuit 100 includes a semiconductor laser 110 formed of a nanowirearray structure 112 at its core, wherein the laser 110 is monolithicallygrown on a (001) Silicon substrate 102. In operation, with an electricvoltage applied to the laser 110, an electric current is injected intothe laser 110 through a p-contact metal electrode 114 and a n-contactmetal electrode 116. In the illustrated example, the laser 110 isconfigured as an edge-emitting laser, such that light 134 that isemitted from the laser 110 and travels along a waveguide 130 (also partof the circuit 100) from which the light exists (as light 136) and isabsorbed by a photodetector 120 (also part of the circuit 100). Thelight 136 absorbed by the detector 120 may be the same light 134 emittedby the laser 110. Note that throughout this disclosure the termsdetector, photodetector, and photodiode are used interchangeably.

The photodetector 120 is formed of a nanowire array structure 122. Inthe illustrated example, the nanowire array structure 112 of the laser110 and the nanowire array structure 122 of the photodetector 120 areidentical. However, in other implementations, the nanowire arraystructure 122 may be a different structure with different compositionsand different design than the nanowire array structure 112. Depicted arealso a p-type metal electrode 124 and an n-type metal electrode 126 ofthe photodetector 120.

The photonic integrated circuit 100 is a monolithically grown circuit,where the semiconductor laser 110 and the semiconductor photodetector120 have been monolithically grown on (001) Si substrate. As describedfurther, the semiconductor laser 110 may operate under a continuous wave(CW) mode of operation for extended periods of time (˜1000 hours ormore). Both the laser 110 and the photodetector 120 are thermally stableand their functionality and performance are stable with increasingtemperatures. The semiconductor laser 100 may be monolithically grownhaving different epitaxial crystal layers forming the heterostructure,which depending on their composition and structure will emit (absorb) atdifferent wavelengths, including the desirable wavelength of ˜1.3 μm. Inthis way, the present techniques provide a first of its kind and tunabledesign photonic devices and photonic integrated circuit grownmonolithically from a Silicon substrate.

FIG. 2 depicts a more detailed illustration of the monolithic nanowirearray quantum semiconductor laser 110 monolithically grown on a (001)Silicon substrate. An array 210 (also termed herein a cluster) of fourindividual nanowire structures 220 that are part of the densely packednanowire array structure 112, where these nanowire structures are grownmonolithically on the Si substrate 102, e.g., using a single stepepitaxial growth process or in some examples using a multiple stepepitaxial growth process.

In the illustrated example, the semiconductor laser 110 is anedge-emitting type of laser device. This type of edge-emittingsemiconductor laser 110 typically has two mirror facets. In FIG. 2,according to one possible example, a mirror facet 242 (not visible inthe drawing) of the laser device 110 points in the direction of thewaveguide structure 130 and another mirror facet 244 of the laser device110 points in the opposite direction which could be pointing intoanother waveguide structure or, as depicted in this particularembodiment, emit light into the air in the form of a beam of light 202.The nanowire array structure 112 emitting in the NIR, e.g., at or around1.3 μm, may have unique nanowire heterostructures that include (i) InNdisks forming the quantum active region and (ii) graded InGaN regionsfor strain balancing in the heterostructure, reduction of defect densityand optimal guiding of light in the lasers and detectors.

In telecommunication applications a semiconductor laser with an emissionwavelength at or around 1.3 μm can be used in single-mode or multi-modecommunication. The laser devices which are described in this disclosuredemonstrate a wavelength of emission at or around this important 1.3 μmwavelength. However, this same technology that is described in thisdisclosure can be used to fabricate semiconductor lasers, grownmonolithically on Si substrate, that have a wavelength of emission at oraround other wavelengths including 1.55 μm. Such devices operating atthe wavelength of ˜1.55 μm, and grown monolithically on Siliconsubstrate, may be useful in long-haul fiber-optic links within the datacommunication and telecommunication industries.

More broadly, the techniques described herein may be used for any typeof photonic integrated circuit. Silicon ComplementaryMetal-Oxide-Semiconductor (CMOS) microchip applications can now beachieved using epitaxial growth and monolithic growth and integration ofsemiconductor lasers and optical detectors with guided wave componentson a (001) Si wafer, with components preferably operating in thewavelength range of 1.3 μm to 1.55 μm at room temperature. Techniquesdemonstrated in the past for having optically pumped or electricallypumped GaAs and InP based semiconductor lasers on Silicon included waferbonding, selective area epitaxy, epitaxy on tilted substrates, and useof quantum dot or planar buffer layers. The present techniques, however,provide a monolithic optical interconnect on a (001) Si substratecomprising of a nanowire array edge emitting electrically pumpedsemiconductor laser and guided wave photodetector, with a planardielectric waveguide in between the laser and the photodetector. Thelaser and the photodiode devices are realized with the same nanowireheterostructure by one-step epitaxial crystal growth process, as furtherdescribed below. An example structure is a III-Nitride dot-in-nanowirearray edge emitting semiconductor laser and guided wave photodetector,with a planar SiO₂/Si₃N₄ dielectric waveguide in between the laser andthe photodetector.

Further still, the present techniques may be used to form lasers ininter-chip or intra-chip communication applications, such as thoserelated to optical communication applications. Semiconductor lasers withemission wavelength at 1.3 μm are desirable as this particularwavelength produces least dispersion in SiO₂ and is transparent toSilicon. This wavelength also allows eye-safe operation. Hence theemitted light has negligible attenuation in Si-based devices and moresignals (or channels) can be accompanied if the light is guided usingSiO₂ based waveguides. Making such an electrically pumped semiconductorlaser directly and monolithically on Silicon has proven to be a greatchallenge to the photonic industry.

While the primary examples described are that of NIR emissions andphotodetection, the techniques may be used to form monolithically grownnanowire semiconductor lasers emitting over a range of frequencies,including in a green region of the spectrum, a red region of thespectrum, and infra-red region of the spectrum. Particular examplesinclude emissions at or about 1.3 μm, at or about 560 nm, at or about610 nm, at or about 630 nm.

We now turn to describing monolithic growth techniques and furtherexample photonic devices that can be formed of nanowire structures grownin accordance with the techniques herein.

Since Silicon (Si) with an indirect bandgap is an inefficientlight-emitting semiconductor. The common technique of incorporating anelectrically-pumped laser on a Silicon platform has been the integrationof III-V based devices on it, either by direct epitaxy or by waferbonding techniques. Direct epitaxial growth of III-V materials andheterostructures on Silicon presents three challenges. A usually largelattice mismatch leads to a high density of threading dislocations.There is also a thermal mismatch due to unequal thermal expansioncoefficients. Finally, the epitaxy of polar III-V materials such as GaAson non-polar Si leads to the formation of antiphase domains (APDs). Thisis usually alleviated by growing the III-V heterostructure on a (001) Sisubstrate offcut by 4° toward the [011] plane. It is unlikely that CMOSand related Si-based technologies will be developed on such tiltedplatforms. Selective area epitaxy and growth on special buffer layershave led to some success.

A different approach to solving the Si and III-V mismatch problem is touse entirely different semiconductors, the III-nitride compounds, butnot in their usual planar form. (Al, Ga, In)N nanowires and nanowireheterostructures grown catalyst-free on (001) Si substrates have shownextraordinary promise as crystalline (wurtzite) nanostructures for therealization of visible light-emitting diodes (LEDs) and diode lasers. Wedemonstrate the application of such nanowires, grown on silicon, tonear-infrared (1.3 μm) lasers and photodetectors. Without any patterningon the substrates the nanowires grow as a random array along the c-axisand are relatively free of extended defects due to the largesurface-to-volume ratio and the formation of a thin SiN_(x) layer at thenanowire-Silicon interface.

The SiN_(x) layer reduces the ˜13.5% stress and reduces the defectdensity at the interface. Compared to planar heterostructures, thenanowires have reduced polarization field due to radial relaxation ofstrain during epitaxy. Consequently, the radiative recombination timesare smaller than in quantum wells. Thin (2 nm to 3 nm thick) single ormultiple InGaN disks can be incorporated along the length of thenanowires and the alloy composition in the disk region can be varied toyield optical emission ranging from the ultraviolet (UV) tonear-infrared (near-IR). It has been established that a quantum dot isformed in the disk region, possibly due to strain relaxation along thesurface of the nanowire during epitaxy. It has also been reported thatthe surface recombination velocity of GaN nanowires is small and about˜10³ cm/s. In contrast to conventional techniques, the self-organizedrandom array of nanowires can be grown on any size of Si substrate,depending on the growth facility, and the process is therefore scalable.The nanowire area density can be varied in the range of 10⁷ cm⁻² to 10¹¹cm⁻² by tuning the growth parameters. Sections of the nanowires can bedoped n-type and p-type and thereby diodes can be realized.

The unique properties of structures such as III-Nitride nanowire andtheir heterostructures make possible the realization of nanowire-basedphotonic integrated circuits with active devices on a (001) Si substrateplatform. Of particular interest is a monolithic optical interconnectconsisting of a diode laser, a passive waveguide or other guided-waveelements, and a photodiode. As used herein, the terms “diode laser”,“laser”, “laser diode”, and “semiconductor laser” are usedinterchangeably. With modulation of the semiconductor laser, thisexample photonic integrated circuit would constitute an opticalcommunication system

FIG. 3A depicts a SEM image of a ridge waveguide semiconductor laser 310that is grown monolithically on a Si substrate 312. FIG. 3B depicts aSEM image of GaN nanowire array structure depicting multiple nanowirestructures clustered together to form a densely packed nanowire arraystructure. The laser 310 in this example is approximately about 50 μmwide. A p-type metallic contact 314 and an n-side metallic contact 316,similar to that of FIG. 1, are also shown in addition to a portion of afront mirror facet 344.

The laser 310 is formed for a nanowire array structure 320 includesdensely packaged array of individual nanowires 340 monolithically grownon the Si substrate 312. An interface region 322 is shown between thenanowire array 320 and the Si substrate 312.

FIG. 4 illustrates the epitaxial crystal structure 400 of a nanowiresemiconductor laser designed for emission at a wavelength at or about1.3 μm. As used herein, references to emissions (or absorptions) “at orabout” or “approximately” or “˜” 1.3 μm refers to emissions (orabsorptions) at 1.3 μm±0.05 μm. Emissions (absorptions) at 1.3 μm arepreferred for telecommunication applications and Si CMOS fabrication.The various crystal layers within the nanowire structure are depicted,showing the different layer compositions. What is depicted in thediagram is the epitaxial crystal structure of an individualInN/In_(0.4)Ga_(0.6)N/GaN nanowire structure, which may be includedwithin an array of densely packaged nanowire structures monolithicallygrown on (001) Si substrate, such as substrate 402. The first epitaxialcrystal layer that is grown directly on top of the (001) Si substrate402 is a 10 nm thick n⁺-GaN layer 404. This is followed by a 250 nmthick n-GaN layer 406. Ten (10) semiconductor crystal layers 408, inthis example comprising of In_(x)Ga_(1−x)N material of variouscompositions in which the Indium (In) content portion, are grown. Asindicated, for the In_(x)Ga_(1−x)N layers x varies from about 0.04 to0.4. The layers of 408 form a graded layer region of theheterostructure, where each of the 10 layers shown has different In andGa concentrations, where in the illustrated example those concentrationsincrease/decrease with each successive layer. The thickness of each ofthese ten layers of In_(x)Ga_(1−x)N is about 15 nm.

An InN/InGaN active region 410 is then formed. In the illustratedexample, the active region 410 includes 4 layers of InN each about 6 nmthick. These InN layers are surrounded by In_(0.4)Ga_(0.6)N barrierlayers of about 12 nm thickness. The InN layers comprise the quantumstructures which in this embodiment, and according to example, arequantum disk. Grown on top of the active region 410 are tensemiconductor crystal layers 412, which form a graded layer region. Inthe illustrated layers 412 are formed of In_(x)Ga_(1−x)N material ofvarious compositions in which the Indium (In) content portion, asindicated, x, in In_(x)Ga_(1−x)N, varies from about 0.04 to 0.4. Thethickness of each of these ten layers of In_(x)Ga_(1−x)N material isabout 15 nm. At the top of the nanowire structure are grown the p-typeGaN layers 414 which, in this embodiment and according to an example,comprise of a 40 nm thick p-GaN layer followed, at the top of thenanowire structure, by a 10 nm thick p⁺-GaN layer.

An example fabrication of a graded refractive index separate confinementheterostructure (GRIN-SCH) nanowire structure 400 is as follows. Thenanowire structure 400 was monolithically grown by plasma-assistedmolecular beam epitaxy (PAMBE) on (001) Si substrates in a Veeco GEN IIsystem. In this fabrication example, the entire nanowire structure 400was grown with a nitrogen plasma flow rate of 1 sccm. GaN sections 404,406, and 414 were grown at a substrate temperature of 820° C., exceptthe top p⁺-GaN region of 414, which was grown at 800° C. The gradedIn_(x)Ga_(1−x)N regions (0≤×≤0.4) 408, 410, and 412 forming thesurrounding graded layers and active region were grown in 10 equal stepsof 15 nm on both sides of the gain region consisting of 4 InN disks ofthickness 6 nm surrounded by 12 nm In_(0.4)Ga_(0.6)N barriers 410. Thegraded regions were grown at substrate temperatures varying from 631° C.(In_(0.4)Ga_(0.6)N) to 819° C. (GaN) and the entire InN-disk andIn_(0.4)Ga_(0.6)N-barrier region was grown at 489° C. The Gallium (Ga)and Indium (In) fluxes were in the range of 1.1×10⁻⁸ to 1.2×10⁻⁷ Torrand 2×10⁻⁸ to 1×10⁻⁷ Torr, respectively, depending on the composition ofthe material being grown. The height, diameter and density of thenanowires are estimated to be ˜400 nm, ˜60 nm, and ˜3.2×10¹⁰ cm⁻²respectively, and the fill factor is estimated to be 0.91.

In examples herein, the 1.3 μm semiconductor laser may have an activearea (laser gain region) that includes a particular type of quantumstructure referred to as quantum dot structure. The particular type ofquantum dot structure may be a quantum disk structure, which is onevariety of quantum dot structure. These quantum disks, in someimplementations, are comprised of InN material surrounded by InGaNbarriers. Such active InN quantum disks have been incorporated innanowire structures for the first time, as a result of the presenttechniques.

Instead of traditional planar epitaxial layers, nanowire structures withquantum disks were used for the laser gain material. Use of nanowirestructures reduces strain in the heterostructure layers of the laser,which has enabled the inventors to incorporate Indium Nitride (InN)quantum disks that can emit light at near-infrared wavelengths includingat the wavelength of, at or around, 1.3 μm. The reduction of strain,through the use of the nanowire structures, also has made it possiblefor these devices to operate under CW mode of operation for extendedperiods of time (e.g. ˜1000 hours or more). At the same time theselasers can operate at elevated temperatures. Indicative of this is therelatively high characteristic temperature, also referred to as theT-zero (T₀) parameter, of these lasers. A high T₀ value indicates thatthe performance of the laser decreases less rapidly with increasingtemperatures. These nanowire structure laser devices are thermallystable devices and their performance does not degrade significantly withincreasing temperatures, another feature heretofore unattainable withconventional techniques.

Example quantum structures that may be used to form the laser gainregions include quantum disks, as well as other quantum dot structures,including quantum spheres, quantum disks, core-shell quantum structures,or other similar forms of quantum elements and/or quantum structures.The term quantum dot is herein used to refer to all these variouspossible shapes of quantum structure within the nanowire structure, oneparticular type of which, according to an example, is the quantum disk.As such, any of the techniques and devices herein may be implementedusing any of a variety of quantum structures, and are not limited onlyto quantum disks.

The quantum structures herein may be disk-in-nanowire (DINW) structuresgrown using state-of-the-art plasma assisted molecular beam epitaxy(MBE). The term DINW refers to nanowire structures which have quantumdisks embedded within them. From transmission electron microscopy (TEM)images it has been demonstrated that these quantum disks form quantumdot type of structures, which further improve the devicecharacteristics. The nanowire structures were grown in a nitrogen plasmarich environment on a (001) Silicon substrate. Typical nanowireheterostructures consist of a graded cladding layer that reduces thestrain and improves the light confinement. As stated before, to achievenear-infrared emission while keeping the advantages of quantumconfinement, InN disks were grown between In_(0.4)Ga_(0.6)N barriers.Such demonstration of InN disk-in-nanowires is the first and only one ofits kind. The InN/InGaN quantum disks have excellent optical properties,which are exploited in the lasers.

Once the material is grown and characterized, lasers were fabricatedusing a series of steps including Parylene planarization,photolithography, plasma etch, and metallization. These ridge waveguidelasers have 5 μm wide to 50 μm wide laser ridge widths and variablelengths. The laser facets were formed by focused ion beam (FIB) etchingtechnique and subsequent deposition of ZnSe/MgF₂ distributed Braggreflector (DBR) mirrors.

The lasers were characterized in a state-of-the-art optoelectronicslaboratory. Maximum output power was found to be 7 mW. Characteristictemperature of these laser devices was found to be 220 K. Thedifferential gain parameter was found to be 3×10⁻¹⁶ cm². Thedifferential gain was measured using high speed measurement techniquesfrom which the bandwidth of these lasers were also found to be ˜3 GHz.Such characteristic properties of these lasers make them an idealcandidate for silicon photonics based applications. A liquid nitrogencooled Ge detector was used to measure the electroluminescenceproperties of the lasers and the peak emission wavelength at stimulatedemission was found to be ˜1.3 μm which is again ideal for on-chipphotonic applications. The novel active (gain) material, straightforward fabrication process and favorable characteristics can make thesenanowire structure lasers that are grown monolithically on Siliconsubstrate one of the most important elements in silicon photonics.

The technology, the devices, and the methods that are described hereinin this disclosure have several advantages that are apparent. Forexample, as the lasers are grown on (001) Silicon, they areCMOS-technology compatible. Hence the technology can be transferred tothe microelectronics industry. In addition, the III-nitride based lasersdemonstrate high characteristic temperature making them suitable forchallenging environments (e.g. computer servers, automobiles, etc.).Also, the 1.3 μm emission wavelength is ideal for multi-modecommunication applications with the data communication andtelecommunication industries.

In addition to fabricating the entire monolithic photonic integratedcircuit, the present techniques provide for fabricating discretenanowire lasers, detectors, and dielectric waveguides.

In some implementations, fabrication of discrete edge emittingsemiconductor laser devices, which are also referred to as laser diodesor diode lasers, was initiated by planarizing the nanowire array withParylene, which was deposited by physical vapor deposition (PVD) at roomtemperature. It has been reported that Parylene is transparent at thewavelength of about 1.3 μm. Furthermore, Parylene helps to passivate thenanowire surfaces and enhances the internal quantum efficiency by about10% to 12%.

Excess Parylene is etched to expose the nanowire tips, which are treatedwith ammonium sulfide to reduce the p-contact resistance. Ridgewaveguide devices were fabricated by a combination of reactive ionetching (RIE), photolithography and contact metal deposition. TheAluminum (Al) n-ohmic contact was formed on the Si substrate surface andthe Nickel/Gold (Ni/Au) p-ohmic contact was formed on the top to theexposed p⁺-GaN nanowire tips. Ridge widths of 5 μm to 50 μm (for exampleas depicted in FIG. 3A) were defined by etching and cavity lengths of0.5 mm to 2 mm were defined by dicing the substrate. This was followedby planarization with SiO₂ and interconnect and contact pad deposition.The cleaved facets were further polished by focused ion beam (FIB)etching using a Ga source and 3 pairs of MgF₂/ZnSe (237 nm/132 nm)distributed Bragg reflectors (DBR) were deposited on both facets toattain a reflectivity of 88%. The contact geometry was arranged in aground-signal-ground configuration to facilitate high frequency probing.The laser diodes are characterized by a forward turn-on voltage of ˜3 V,a series resistance of 10Ωto 25Ω, and reverse breakdown voltage of 8 Vto 12 V.

FIG. 5 depicts an individual nanowire structure 500 and the epitaxialcomposition of a nanowire structure within the structure of asemiconductor quantum laser grown monolithically on Silicon substrateand emitting at near infra-red wavelength of at or about 1.3 μm. In theillustrated example, grown on a Si substrate 502 is a 260 nm n-GaN layer510. On top of this layer 510, grown in ten steps, is a group 512 of 150nm thick graded cladding layers from n-GaN to n-In_(0.4)Ga_(0.6)N. Ontop of this group 512 of layers are the active region 514 layers. Theactive region 514 of this structure includes 4 layers of InN each about6 nm thick. These InN layers are surrounded by In_(0.4)Ga_(0.6)N barrierlayers of about 12 nm thickness. The InN layers form quantum structureswhich in the illustrated example are quantum disks. On top of the activeregion 516 of the nanowire structure grown is a 150 nm p-GaN layer.

FIG. 6 provides a plot 600 of the experimentally measured Light-Current(L-I) characteristic plots 602 and 604 of broad area near infra-red(NIR) semiconductor laser devices 606 and 608, respectively, each havingemission wavelength of about 1.3 μm. The inset 610 shows the outputwavelength characteristic plot for an injection current of 810 mA. Theplot 600 depicts the steady-state L-I characteristics at roomtemperature of a 50 μm×2 mm ridge waveguide laser device operating underpulsed (5% duty cycle) mode of operation. Output powers up to ˜10 mWwere measured at room temperature without any heat sinking or facetcooling. The output spectrum 612 depicted in the inset 610 confirms 1.3μm peak wavelength of emission. The slope efficiency was 0.14 W/A. A lowvalue of threshold current I_(th)=673 mA was measured. The wall plugefficiency parameter was ˜0.81%.

FIG. 7 is a plot 700 of the temperature dependence of the thresholdcurrent density J_(th). Linear fit line 702 indicates a characteristictemperature T₀=241 K. The data in this diagram are associated withnanowire structures of dimensions as shown. The nanowire structure wasoperated under a 5% pulsed mode of operation. In this example, thenanowire structure was formed as a laser having an emission wavelengthin the near infra-red range of the spectrum at a wavelength of at orabout 1.3 μm.

FIG. 8 illustrates a plot 800 of the measured output power of a 1.3 μmwavelength disk-in-nanowire semiconductor laser as a function of timewith constant Continuous Wave (CW) current injection. These measurementswere made without any heat sinking or active cooling. The plot 800indicates a lifetime of ˜1000 hours. Nanowire semiconductor lasers grownmonolithically on Silicon substrate have the potential for much higherlifetimes than what is depicted here. In this example, the nanowirestructure or array based laser has dimensions of 5 μm width by 500 μmcavity length. The device is operating at a temperature of 300 K and ata CW current of 20 mA.

The fabrication of the photonic integrated circuit follows similarprocess steps to the fabrication of discrete devices. The details of anexample photonic integrated circuit fabrication process are describedfurther below. A SEM image of the entire photonic circuit 900 isdepicted in FIG. 9 wherein a laser 902, a waveguide 904, a detector 906,a p-contact 908 and a n-contact 910 for current injection are indicated.In the fabrication of the photonic integrated circuit 900, thedielectric waveguide 904 which is in between the nanowire laser 902 anddetector 906 is formed by selective etching of the nanowires and thedeposition of 400 nm SiO₂ followed by 400 nm of Si₃N₄. For the laser902, the mirror facet away from the waveguide (not visible) was madereflective by FIB etching and subsequent deposition of MgF₂/ZnSe DBRlayers and the mirror facet 912 coupled to the waveguide 904 was madereflective with 4 pairs of air/nanowire-Parylene DBR layers 914 (seeinset image 916), also formed by FIB etching. For the detector 906, ˜220nm of anti-reflective SiO₂ was deposited on the facet of the detectorthat is not coupled to the waveguide.

FIGS. 10A and 10B depict a SEM image (top image FIG. 10A) and an opticalmicroscope image (bottom image FIG. 10B) of a photonic integratedcircuit structure 1000, respectively. The photonic integrated circuit1000 may be like that of device 900 shown in FIG. 9. The SEM image ofFIG. 10A depicts a planar top view SEM image of the device.

In the illustrated example of the photonic integrated circuit 1000,there is a semiconductor laser 1002, a linear waveguide structure 1004,and a semiconductor photodetector 1006 fabricated in a linearly alignedarrangement. Also indicated are two p-contact metallic pads 1008 and1010 and two n-contact metallic pads 1012 and 1014. Also indicated isthe mirror facet 1016 of the laser 1002. The semiconductor laser 1002and the semiconductor photodetector 1006 are both III-GaN nanowire arraystructures that are formed monolithically on a Silicon substrate.

FIG. 11 depicts a process flow chart showing a fabrication process 1100of fabricating a photonic integrated circuit. The method that isdepicted is according to an example implementation. At a block 1102, theepitaxial deposition of the first GaN template layer onto the Silicon(Si) substrate is performed. At a block 1104, the epitaxial depositionof the additional n-type layers of the crystal structure onto the GaNcoated Si substrate is performed. At a block 1106, epitaxial depositionof the first group of graded In_(x)Ga_(1−x)N layers forming thewaveguide is performed. At a block 1108, the epitaxial deposition of thequantum structure layers of the nanowire structure is performed. At ablock 1110, the epitaxial deposition of the second group of gradedIn_(x)Ga_(1−x)N layers forming the waveguide is performed. At a block1112, the epitaxial deposition of the additional p-type layers of thenanowire structure is performed. At blocks 1102 to 1112 the processesassociated with the epitaxial crystal growth process phase of thefabrication process are shown. Below are described examples associatedwith the device fabrication phase of the fabrication process 1800.

At a block 1114, the planarization of the nanowire array structure, bydeposition of Parylene material and subsequent etching of excessParylene material is performed. At a block 1116, the deposition of thep-metal contact layer over selected areas of the nanowire structurearray is performed. At a block 1118, the selective etching of the arrayto form ridge waveguide structure of the devices is performed. At ablock 1120, another etching step to expose the part of the Si betweenthe ridges and etch the nanowires between the laser and detector isperformed. At a block 1122, the deposition of the n-metal contact overselected areas of the exposed n-Silicon is performed. At a block 1124,the deposition of waveguide layers in the region between the laserdevice and the photodetector device is performed. At a block 1126, theformation of one mirror facet of the laser through Focused Ion Beam(FIB) etching and subsequent deposition of Distributed Bragg Reflector(DBR) layers on the mirror facet is performed. At a block 1128,formation of anti-reflective layer on one side of the detector facetthrough the deposition of SiO₂ is performed. At block 1130, theformation of the other mirror facet of laser by FIB etching of thenanowire-Parylene composite and as a result forming air-semiconductorDBR layers are performed. The end result of the above mentionedprocesses of is the realization of the photonic integrated circuit.

FIGS. 12A and 12B depict part of the fabrication process 1100 of forminga photonic integrated circuit 1200 (see, FIG. 15). The figures show thegrowth of a nanowire array structure 1202, formed of individual nanowirestructures 1204, grown monolithically on Silicon substrate 1206. FIG.12A depicts the crystal growth of the nanowire structures on n-type(001) Si substrate using plasma assisted molecular beam epitaxy (PA-MBE)technique. FIG. 12B depicts a Parylene planarization of the nanowirearray structure 1902, in which a Parylene material layer 1208 fills theempty space between the individual nanowire structures 1204.

FIGS. 13A and 13B depict further processes of the growth of the nanowirestructures on Silicon substrate 1206 and the formation of amonolithically grown photonic integrated circuit on a Silicon substrate.FIG. 13A depicts the process of p-metal deposition over selected areasof the nanowire structure array. A p-metal contact 1210 selectivelycovers some regions of the nanowire array 1202 while leaving exposedother regions 1212, where the exposed regions are exposed regions ofParylene in the illustrated example. FIG. 13B depicts the process ofetching of the nanowire structure array 1202 in order to form channelson the sample between the regions where there are located a laser 1214and a photodetector 1216. An etched channel 1218 is shown. FIG. 13Billustrates two p-contact metallic electrode 1210, one electrode for thelaser 1214 and the other for the photodetector 1216.

FIGS. 14A and 14B depict further processes for the monolithic growth ofthe nanowire structures on Silicon substrate and the formation of amonolithically grown photonic integrated circuit on a Silicon substrate.FIG. 14A depicts the process of n-metal deposition over selected areasof the exposed n-Silicon substrate 1206. An exposed area 1220 wascreated by the FIB etching process of FIG. 13B. The Parylene material1208 that fills the empty area between the individual nanowirestructures of the array 1202 is shown. A n-metal contact 1222 depictedhere is Aluminum (Al) according to an example. The p-metal contact 1210that is deposited over the detector 1216 is comprised of Nickel (Ni) andGold (Au) layers according to an example. The n-metal contact 1222 iscomprised of Aluminum (Al). FIG. 14B depicts the process of waveguidelayers deposition in the region between the laser 1214 and thephotodetector 1216. In this example, a waveguide structure 1224 isformed and comprises 400 nm thick SiO₂ bottom layer 1226 and 400 nm ofSi₃N₄ top layer 1228. FIG. 15 provides a final schematic of the photonicintegrated circuit 1200 formed by these processes. The laser 1214produces an output emission 1230 at or about 1.3 μm. Output light 1230is emitted from the laser 1214, travels through the waveguide structure1224, and upon reaching the detector 1216 is absorbed as the inputlight.

As shown, the inventors have formed both laser and photodetectorsemiconductor photonic devices on (001) Si substrate in a monolithicfashion. The present techniques successfully demonstrate the coupling ofthe edge emitting laser emission into a monolithic dielectric waveguideand a subsequent coupling of the guided light into an in-plane guidedwave photodiode (also referred to as photodetector). Either passivewaveguides, such as those described, or other guided wave components canbe used to form parts of an optical interconnect on a Silicon chip. Thebottom-up monolithic approach demonstrated here allows optoelectronicintegration with Si-based electronic circuits for laser biasing,modulation, and other controls. By virtue of the low growth temperatureat which the nanowire heterostructures are grown it is expected that theintegration will be compatible with CMOS processing of the electronics.

The present techniques show III-nitride nanowire lasers and photodiodesdesigned with nanowires having identical heterostructures andconstituent materials section. Hence they can be realized by one-stepepitaxy on (001) Si, adding significant flexibility to device andcircuit fabrication. The nanowire heterostructure may include InN disksquantum regions and graded InGaN regions. Indeed, the present techniquessuccessfully demonstrated the first use of pure InN quantum disks as theactive region of III-nitride nanowire devices. While the large In fluxrequired during epitaxy can substantially increase radial growth rate,inducing coalescence of adjacent nanowires, and such coalescence candeteriorate the optical quality (luminescence efficiency) of thenanowire array, the present techniques include all new growthparameters, e.g., compared to the ones used in nanowire growth forvisible lasers. The results, including the formation of pure InN quantumdisks, was unexpected. The In and Ga metal fluxes have been reduced byalmost one order of magnitude compared to metal fluxes used in Ga-richgrowths. To ensure low desorption of the metals, the growth temperaturewas also been reduced accordingly. The growth temperatures are almost 50to 100 C. lower than the temperatures used in visible (Ga-rich) nanowiregrowth. The result has been the monolithic fabrication of a nanowirearray based photonic integrated circuit having a laser, waveguide and aphotodiode.

As will be appreciated, the present techniques provide considerableuniqueness and advantage over conventional concepts of nanowirefabrication, where some have proposed nanowire structures but withlimited success and mostly applying what appears to be theoreticalapproaches, unsupported by actual fabrication. U.S. Pat. Nos. 8,212,235,8,932,940, and 7,474,811, for example, provide merely general, and inplaces vague, concepts of nanowire optoelectronic devices, without anyreal examples. Their proposed nanowires are in a bridging configurationimpractical to fabrication, and in configurations that suggest thatmonolithic nanowire structures are not even possible. Moreover, in mostof the proposed devices, charged carriers (electrons and holes) andphotons propagate along the axis of the nanowires and hence theoptoelectronic devices are vertical and top-emitting or top-absorbing,which means the devices were confined to placement on (111) and (110)silicon and not compatible with CMOS technology and silicon photonicsand (001) monolithic fabrication.

While examples herein are provided showing nanowires structuresmonolithically growth as dot-in-nanowire structures, other quantumactive region configurations may be used such as core-shell nanowires.Further still, the present techniques may be used to fabricate thenanowire arrays and individual nanowire structures using a metallic maskwith patterned holes used on the substrate in order to define the shapeand the dimensions of the nanowire structures. It is possible to adopt amethod of precisely controlling the formation of nanowire structureswith precise predetermined diameter, height, spacing, and separation.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, may also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the description. Thisdescription, and the claims that follow, should be read to include oneor at least one and the singular also includes the plural unless it isobvious that it is meant otherwise.

This detailed description is to be construed as an example only and doesnot describe every possible embodiment, as describing every possibleembodiment would be impractical, if not impossible. One could implementnumerous alternate embodiments, using either current technology ortechnology developed after the filing date of this application.

What is claimed:
 1. A semiconductor device comprising: a Silicon (Si)substrate; and a III-Nitride nanowire structure having (i) a quantumregion formed of one or more layers of InN quantum disks, (ii) a firstgraded layer region, and (iii) a second graded layer region, wherein thequantum region is located between the first graded layer region and thesecond graded layer region, and wherein the III-Nitride nanowirestructure is monolithically grown from the Si substrate, and wherein theIII-Nitride nanowire structure is responsive at or about 1.3 μm.
 2. Thesemiconductor device of claim 1, wherein quantum region comprises aplurality of InN quantum disk layers each having at least one quantumdot, at least one quantum arch-shaped form, at least one quantum dotwithin a quantum disk, at least one core-shell quantum structure, or acombination of thereof.
 3. The semiconductor device of claim 2, whereineach of the plurality of InN quantum disk layers has at least onequantum dot.
 4. The semiconductor device of claim 3, wherein each of theplurality of InN quantum disk layers is separated by an In_(x)Ga_(1−x)Nbarrier.
 5. The semiconductor device of claim 1, wherein the III-nitridenanowire structure is an In-N nanowire structure, wherein the firstgraded region comprises a plurality of n-type In_(x)Ga_(1−x)N layers,and the second graded region comprises a plurality of p-typeIn_(y)Ga_(1−y)N layers.
 6. The semiconductor device of claim 5, where xis different for each of the plurality of n-type layers and wherein y isdifferent for each of the plurality of p-type layers.
 7. Thesemiconductor device of claim 1, further comprising: a lower regionformed of one or more n-type GaN layers grown between the Si substrateand the first graded layer region; and an upper region formed of one ormore p-type GaN layers grown on the second graded layer region.
 8. Thesemiconductor device of claim 1, wherein the III-Nitride nanowirestructure is formed as a nanowire semiconductor laser.
 9. Thesemiconductor device of claim 1, wherein the III-Nitride nanowirestructure is formed as an edge emitting nanowire semiconductor laser.10. The semiconductor device of claim 1, wherein the III-Nitridenanowire structure is formed as vertical surface emitting nanowiresemiconductor laser.
 11. The semiconductor device of claim 1, whereinthe III-Nitride nanowire structure is formed as a nanowire semiconductorphotodetector.
 12. The semiconductor device of claim 1, furthercomprising a Silicon Nitride layer coated on the Si substrate, such thatthe III-Nitride nanowire structure is monolithically grown from the Sisubstrate via the Silicon Nitride layer.
 13. The semiconductor device ofclaim 1, further comprising a Gallium Nitride layer coated on the Sisubstrate, such that the III-Nitride nanowire structure ismonolithically grown from the Si substrate via the Gallium Nitridelayer.
 14. The nanowire array structure of claim 1, wherein theplurality of III-Nitride nanowire structures form a nanowiresemiconductor laser.
 15. The nanowire array structure of claim 1,wherein the plurality of III-Nitride nanowire structures form an edgeemitting nanowire semiconductor laser.
 16. The nanowire array structureof claim 1, wherein the plurality of III-Nitride nanowire structuresform a nanowire semiconductor photodetector.
 17. A Nanowire arraystructure comprising: a Silicon (Si) substrate; and a plurality ofIII-Nitride nanowire structures each having (i) a quantum region formedof one or more layers of InN quantum disks, (ii) a first graded layerregion, and (iii) a second graded layer region, wherein the quantumregion is located between the first graded layer region and the secondgraded layer region, wherein the plurality of III-Nitride nanowirestructures are monolithically grown from the Si substrate, and whereinthe plurality of III-Nitride nanowire structures are responsive at orabout 1.3 μm.
 18. A photonic integrated circuit comprising: a Silicon(Si) substrate; a first plurality of III-Nitride Nanowire structureseach having (i) a quantum region formed of one or more layers of inNquantum disks, (ii) a first graded layer region, and (iii) a secondgraded layer region, wherein the quantum region is located between thefirst graded layer region and the second graded layer region, whereinthe first plurality of III-Nitride nanowire structures aremonolithically grown from the Si substrate, and wherein the firstplurality of III-Nitride nanowire structures form a nanowiresemiconductor laser capable of emitting a photonic output at or about1.3 μm; and a second plurality of III-Nitride nanowire structures eachhaving (i) a quantum region formed of one or more layers of InN quantumdisks, (ii) a first graded layer region, and (iii) a second graded layerregion, wherein the quantum region is located between the first gradedlayer region and the second graded layer region, wherein the secondplurality of III-Nitride nanowire structures are monolithically grownfrom the Si substrate, and wherein the second plurality of III-Nitridenanowire structures form a nanowire semiconductor photodetector capableof absorbing a photon input at or about 1.3 μm.
 19. The photonicintegrated circuit of claim 18, wherein the nanowire semiconductor laserand the nanowire semiconductor photodetector have the sameheterostructure.
 20. The photonic integrated circuit of claim 18,wherein the nanowire semiconductor laser and the nanowire semiconductorphotodetector are formed using a single-step selective-area growthepitaxial process.
 21. The photonic integrated circuit of claim 18,wherein the nanowire semiconductor laser and the nanowire semiconductorphotodetector are formed using a multiple-step selective-area growthepitaxial process.
 22. The photonic integrated circuit of claim 18,further comprising a waveguide deposited on the Si substrate between thenanowire semiconductor laser and the nanowire semiconductorphotodetector, wherein the waveguide is configured to propagate thephotonic output from the nanowire semiconductor laser to the nanowiresemiconductor photodetector.